The present invention relates to cleaning a substrate.
In the manufacture of integrated circuits, active devices are formed on a substrate by alternately depositing and etching layers of dielectric, semiconducting, and conducting materials, such as silicon dioxide, polysilicon, and metal compounds and alloys. These layers are etched to form a pattern of etched features, by providing a resist layer of photoresist and/or oxide hard mask on the substrate and using lithography, for example, to expose and pattern the resist layer. The portions of the layers adjacent to the patterned resist features are etched to form a predefined pattern of gates, vias, contact holes, trenches, and/or metal interconnect lines. Etching is typically performed using a capacitively or inductively coupled plasma of halogen-containing gases, as for example described in Silicon Processing for the VLSI Era, Vol. 1, Chapter 16, by Wolf and Tauber, Lattice Press, 1986, which is incorporated herein by reference in its entirety.
After the etching process, etchant residue and remnant resist material that remain on the substrate are removed prior to processing of the next layer on the substrate. The etchant residues formed during the etching processes are typically complex compositions that condense from the vaporized plasma environment onto the freshly etched features and other surfaces of the substrate. The composition of the etchant residue depends upon the composition of the etching gas, the vaporized species of the layer that is being etched, and the composition of the organic resist or hard mask layer that is sputtered or etched away by energetic plasma ions. Vias are plugs of conducting material that electrically connect to a metal interconnect line underlying the dielectric layer. Vias are formed by etching a hole or void into the dielectric layer, and subsequently filling the hole with a conducting material.
One method of cleaning or removing the residue material is a dry cleaning method in which a plasma of a gas, such as oxygen is used to burn off the residue material remaining on the substrate. However, conventional dry clean methods often (i) do not remove sufficient amounts of residue from the substrate, (ii) require extended processing times that decrease process throughput, and/or (iii) can etch into underlying layers on the substrate. Thus, the etchant residue is typically removed by a wet cleaning process in which the substrate is scrubbed in a heated solvent (for example EKC 265, commercially available from Shipley, Co., Newton, Mass.) to dissolve accumulated etchant residue. However, the wet cleaning process often requires a solvent that is costly and hazardous to the environment. Moreover, transferring the substrate from the etching process chamber to a wet cleaning station may lower yields from the substrate if the substrate is contaminated in the transferring operation. Furthermore, exposure of the freshly etched metal features to the atmosphere during transport of the substrate between the different processing stations can oxidize contact/junction points, providing high electrical contact resistances, which are undesirable.
Thus, there is a need to be able to clean a substrate to, for example, remove remnant resist and etchant residue on a substrate. It is further desirable to clean a substrate without damaging the substrate. It is still further desirable to clean a substrate without compromising process throughput.
The present invention satisfies these needs. In one aspect of the present invention a substrate cleaning method comprises exposing a substrate to an energized process gas to remove residue and resist material from the substrate, the process gas comprising cleaning gas and an additive gas comprising NH3.
In another aspect of the invention, a substrate processing method comprises providing a substrate having a dielectric material, exposing the substrate to an energized process gas comprising etchant gas to etch the dielectric material, exposing a substrate to an energized process gas to remove residue and resist material from the substrate, the process gas comprising cleaning gas and an additive gas comprising NH3.
In another aspect of the invention, a method of removing etchant residue or resist material on a substrate comprises exposing the substrate to an energized process gas comprising cleaning gas and NH3 to remove a majority of the etchant residue or resist material.
In another aspect of the invention, a substrate cleaning method comprises exposing a substrate to an energized process gas to remove residue and resist material from the substrate, the process gas comprising cleaning gas. The method also comprises applying a bias to the substrate.
In another aspect of the invention, a substrate cleaning method comprises providing a substrate in a process chamber, and providing an energized process gas comprising cleaning gas in the process chamber to remove residue from the surfaces in the chamber and to remove residue and resist material from the substrate.
In another aspect of the invention, a substrate cleaning method comprises providing a substrate in a process chamber, and providing an energized process gas comprising cleaning gas and a nitrogen-containing gas to remove residue from the substrate and from the surfaces in the chamber, wherein the volumetric flow ratio of nitrogen-containing gas to cleaning gas is less than about 1:1.
In another aspect of the invention, a substrate processing method comprises providing a substrate having a dielectric material in a chamber, providing an energized etchant gas in the chamber to etch the dielectric material, thereby forming etchant residue, and providing an energized process gas to remove etchant residue and resist material from the substrate and to remove etchant residue from surfaces of the chamber, the process gas comprising cleaning gas and an additive gas comprising NH3.